About WITTENSTEIN

Improving lathe performance

DMT Drehmaschinen GmbH manufactures lathes to meet the highest quality standards. Their performance has been significantly improved since the company introduced the Galaxie® Drive System from WITTENSTEIN.

Creating new opportunities

DMT – internationally renowned manufacturer of lathes

DMT Drehmaschinen GmbH of Lörrach, in the far south-west corner of Germany, manufactures lathes for manual, cycle controlled and CNC machining – optionally also with interactive contour programming. In addition to standard machines, which can be upgraded with tool turrets, direct drive tools and power chucks on request, the company also makes special-purpose lathes to customer specifications. Especially when single components or small batches have to be fabricated quickly and extremely precisely, DMT machines are the solution of choice.

Customers demand ever higher machining quality

Machining high quality materials – and responding to demands for ever higher precision – represents a daunting challenge for the machine technology. DMT's engineers were therefore looking for a drive system that could provide better machining quality and higher productivity. The torsional stiffness and backlash of the main motor/gearbox unit were identified as decisive parameters because they have a significant impact on the dynamic positioning accuracy. This, in turn, is one of the keys to machining quality, a longer tool life and higher metal removal rates by the equipment during machining operations with the C axis. Although a rotary direct drive would have been capable of delivering the required power, major changes would have been necessary to the existing machine concept.

Better torsional stiffness and permanent freedom from backlash

The Galaxie® Drive System was integrated into the existing system without any problems, leading to a substantial gain in milling performance. The machining times are now much shorter. Even larger workpieces can be produced in one setting – and in most cases there is no longer any need for additional processing on a separate milling machine. They can also be positioned a good deal faster and more accurately. Owing to the torsional stiffness and freedom from backlash achieved with the Galaxie® Drive System, the tool cutting edges have an extended life and lathe uptime is increased. The Galaxie® Drive System simultaneously sets benchmarks in terms of power consumption, which is far lower than with direct drives.

Revolutionary new and in daily operations

The video explains how the Galaxie® Drive System makes machining times of DMT much shorter.

THE GALAXIE® DRIVE SYSTEM – RECORD BREAKING IN EVERY DISCIPLINE

THE GALAXIE® DRIVE SYSTEM – RECORD BREAKING IN EVERY DISCIPLINE

Galaxie® is a hollow-shaft drive system which fuses a newly developed high performance motor with revolutionary gearbox kinematics.

For the first time ever, a gearbox dispenses completely with a gear wheel – instead, each of the teeth involved in torque conversion is an independent and dynamic entity grouped around a non-circular, three-cam input polygon and guided along the teeth of a ring gear. This principle has the advantage that almost all of the teeth engage simultaneously – compared to only a few with traditional gear types. The tooth geometry moreover corresponds to a logarithmic spiral, so that power is transmitted by surface contact. Benchmark calculations with helical-toothed planetary gearboxes show that the new kinematics give a tooth surface which is 6.5 times larger for the same hollow shaft diameter. This is a crucial aspect that is central to the 170% improvement in torque conversion and the threefold increase in overload protection. Another defining feature of the kinematics is that a hydrodynamic lubrication film is built up by the multiple teeth in surface contact – even at low speeds and up to very high torque loads. Mechanical wear is reduced to a minimum and once the torsional backlash has been set, it remains absolutely constant throughout the lifetime of the equipment.

Due to the novel design principle, there is only a tiny gap between the tooth carrier and the internal ring gear. This clearance is so small that there is practically no bending length. What's more, the teeth in contact are automatically aligned, leading to optimal engagement with the internal gear teeth – and an optimal transverse load distribution. The outcome: a gearbox that is completely backlash-free. Up to 580% more torsional stiffness is achieved compared to existing technologies. The very high stiffness at the zero crossing is retained, even with alternating loads – without any reduction in the maximum transmissible torques.